1. Field of the Invention
The technology disclosed herein generally relates to at least one apparatus and method for detecting targeted materials at security checkpoints or inline screening systems, and more particularly, to an apparatus and method for integrating first threat analysis data with second threat analysis data to provide an accurate and reliable final threat assessment.
2. Discussion of Related Art
With acts of global terrorism on the rise, detection of targeted materials has become increasingly important. Targeted materials may include, but are not limited to, explosives, weapons, and narcotics, among others. Advanced detection systems have been developed that can automatically identify not only the shapes of articles carried within baggage, but also the material characteristics and/or composition of those articles. Such detection systems include computed tomography (CT) scanners, quadropole resonance (QR) scanners, x-ray diffraction (XRD) scanners, and Advanced Technology (AT) scanners.
The performance of these detection systems is measured using three primary parameters, false positive rate, probability of detection, and scanning speed (throughput). Often, the improvement of one parameter occurs at the expense of another.
False positives occur when a detection system incorrectly identifies a harmless object/substance as an actual threat object/substance. False positives are commonly generated because conventional detection systems cannot always correctly distinguish actual threat objects/substances from harmless objects/substances in situations where both types of objects/substances exhibit similar threat characteristics, such as similar density and/or mass.
Detection systems are usually required to have a minimum probability of detection, or detection rate. The detection rate can be determined by systematically inserting objects containing one or more target materials of interest and then measuring the percentage of the times at which the detection system alarms.
Low numbers of false positives and high throughput are required for security checkpoints at public transportation facilities, such as airports. Co-pending U.S. patent application publication No. 2005/0128069 (hereinafter, “'069 publication”), describes how an upstream computed tomography (CT) scanner and a downstream quadropole resonance (QR) scanner, directly connected via a shared conveyor, may be used in sequence to reduce the number of false positives. The CT scanner scans an entire item of baggage and outputs a set of risk values indicative of the presence of particular types of targeted material. This risk values are inputted to the QR scanner, which scans the entire item of baggage a second time, generates its own risk values, and integrates these with the risk values inputted from the CT scanner.
Often, however, a second screening system will have considerable lower throughput than the first screening system. In such cases, it is desirable from a throughput point of view to screen only the part of the scannable object that contains the suspect region identified by the first system. Co-pending U.S. patent application publication No. 2005/0123217 (hereinafter, “'217 publication”) describes a method for improving baggage throughput. The method determines whether and how an item of baggage's position has changed from one detection apparatus to the next, and saves time by permitting a downstream detection apparatus to examine only a particular suspect region within the item of baggage. This method is schematically represented in FIG. 5.
Referring to FIG. 5, a first threat detection apparatus takes a first transmission image 502. In the first transmission image 502, a first suspect region is identified, and a first list 518 of coordinates of the first suspect region is created. The item of baggage is then placed in a second threat detection apparatus, which takes a second transmission image 504 to determine the geometrical transformation between the coordinate systems of the two threat detection apparatuses. Each transmission images 502, 504 is subjected to pre-processing 506, 508, during which geometric rectification and optical pre-processing of intensities may be performed. Various features of the respective image contents are then measured in preparation for performing features extractions 510, 512. Comparative features are then determined and the second position of the scannable object relative to its first position is determined. The extracted features are appraised, and a calculation 514 of the change in position is performed. There is also a geometric transformation 516 of the images. Following the successful determination of position via the calculation 514 of the change of position, a second list 520 of coordinates of a transformed second suspect region is created. The coordinates of the second suspect region are the coordinates of the first suspect region that have been transformed into the second transmission image 504.
Thus, in the known integrated detection system described in the '217 publication, no intelligent fusion of the independent information obtained by the upstream detection apparatus and the downstream detection apparatus is performed. Additionally, the known threat detection system described in the '069 publication scans the entirety of an object multiple times. A need therefore exists for an improved integrated detection system that achieves high throughput with a minimal number of “false positives.”